1. Field of the Invention
The present invention relates to a photoelectric device-part in which a photoelectric device is mounted on a concave part provided in a three-dimensional circuit substrate
2. Description of the Prior Art
Conventionally, a part which emits or receives light using a photoelectric device to convert light into electricity and vice versa is known as a photoelectric device-part. For example, a light emitting device 100 shown in FIG. 17A is a photoelectric device-part in which electrodes 105 and 106 are formed on a substrate 101, an LED (light emitting diode) chip 108 is mounted on the electrode 106 through an electroconductive bonding material 107 to electrically connect a lower surface of the LED chip 108 to the electrode 106, an upper electrode of the LED chip 108 is electrically connected to the electrode 105 by a wire bonding, and the LED chip on the substrate is covered with a case 110 having a centroclinal inner surface, whereby light output from the LED chip is all reflected (for example, Japanese Laid-Open Patent Publication No. 2001-177155).
In addition, a light emitting device 200 shown in FIG. 17B is a photoelectric device-part comprising a substrate 201 formed of almost a flat plate conductor in which a concave part 202 is formed, an insulating film 204 formed thereon, an upper electrode 205 having a wire bonding pad and an electroconductive pattern electrode 206 reaching an inner surface of the concave part 202 from an upper surface of the substrate, in which an electrode on a lower surface of an LED chip 208 is electrically connected to the pattern electrode 206 through a electroconductive bonding material 207 and an electrode on an upper surface of the LED chip 208 is electrically connected to the upper electrode 205 through a bonding wire 209 (for example, Japanese Laid-Open Patent Publication No. HEI 10-098215).
Furthermore, a surface mounting type of chip part 300 shown in FIG. 17C is a photoelectric device-part in which an insulating substrate 301 includes upper electrodes 305 and 306 and lower electrodes 315 and 316 connected thereto and an LED chip 308 is housed in a concave part 302 formed in the insulating substrate 301 (for example, Japanese Laid-Open Patent Publication No. HEI 11-74420). The concave part 302 has four slanting surfaces and a stepwise projection 303 is formed in the middle of one of the slanting surfaces. A bonding pad 325 electrically connected to the upper electrode 305 is formed on an upper surface of the projection 303. In addition, the upper electrode 306 is led to the slanting surface of the concave part 302 and to a bottom surface of the concave part 302. An electrode on a lower surface of the LED chip 308 is mounted on the bottom surface of the concave part 302 through an electroconductive bonding material 307 to be electrically connected to the upper electrode 306. An electrode on an upper surface of the LED chip 308 is electrically connected to a bonding pad 325 through a bonding wire 309. In addition, the LED chip 308 and the bonding wire 309 are sealed with a sealing resin 311.
However, according to the photoelectric device-part shown in FIG. 17A or disclosed in the patent document 1, since a space for a pad of a wire bonding is needed at the bottom surface of the case 110 having the centroclinal inner surface, there is a limit of miniaturization of the substrate. For example, when the substrate is reduced in size, an insulating space between the electroconductive bonding material 107 and the electrode 105 is reduced, which could cause a short circuit. Besides, since the bonding pad and LED chip 108 are positioned at the bottom surface of the case 110, the LED chip 108 is decentered and a light converging property is lowered.
In addition, according to the photoelectric device-part shown in FIG. 17B or disclosed in the patent document 2, since the bonding wire 209 is long, it becomes an obstacle in a light path, which lowers light emitting efficiency in the photoelectric device-part. In addition, in a case where the LED chip 208 is sealed with a resin at a later step, as a wire length increases, it is likely to be affected by expansion and contraction (thermal stress) of the resin and reliability in bonding of die wire bonding is lowered. Besides, in a case where the bonding wire is formed of Au wire, if the wire is long, the costs are increased. Furthermore, when the photoelectric device-part is used as a photoelectric signal converting device, as the bonding wire is increased, L component (inductance) of the bonding wire is increased, which prevents the signal transmission from being speeded up.
Besides, according to the photoelectric device-part shown in FIG. 17C or disclosed in the patent document 3, since it is necessary to provide an area for the stepwise projection 303 provided in the middle of the slanting surface, which limits the miniaturization of the photoelectric device-part. In addition, when the projection 303 is provided, a sectional area of the concave part 302 becomes large, which damages light converging property (usability efficiency). In addition, since the LED chip 308 is decentered, that is, not disposed at the center of the opening surface of the concave part 302, whereby light converging property is lowered.